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1. What is the difference between d.c. and a.c? Direct current passes in the same direction Alternating current constantly changes direction. 2. How does a circuit breaker work? When a current is too great the live wire breaks in the circuit breaker. 3. What is the advantage of a circuit breaker over a fuse? You can reset a circuit breaker rather than having to replace a whole fuse. 4. How does a fuse work? If the current in a fuse is too high the fuse melts breaking the circuit. 5. What does P = I x V work out? Power = current x voltage 6. What does P = E / t work out? Power = energy / time 7. Draw and label the structure of an atom 8. How are ions formed? An atom loses or gains electrons 9. How can we identify an alpha particle? 2 neutrons + 2 protons. The same as a helium nucleus. 10. How can we identify a beta particle? Electron from the nucleus 11. What is the half life of a substance? Average time for the number of nuclei of the isotope in a sample to halve. 12. What is nuclear fission? Splitting of an atomic nucleus 13. What is nuclear fusion? Joining of two atomic nuclei together 14. How do alpha, beta and gamma radiation differ in penetration power? Alpha and beta can be deflected by both electric and magnetic fields. Gamma cannot. 15. What is an isotope? An atom with a different number of neutrons, but same number of protons and electrons. 16. How can we identify a gamma particle? EM radiation 17. What must happen for nuclear fission to occur in a radioactive ample? Must absorb a neutron. 18. What happens to material that gains electrons? It becomes negatively charged. 19. What happens for an insulator to become negatively charged? An excess of electrons 20. What material gains a charge? An insulator 21. What happens for an insulator to become positively charged? A lack of electrons relative to protons 22. What happens when you bring together two objects with like charges? They repel 23. What happens when you bring together two objects with opposite charges? They attract 24. How would you calculate resistance? Potential difference = current x resistance 25. What is the purpose of defibrillation? Delivers a controlled electric shock to a heart to restart it. 26. What does the electric shock do to the heart in defibrillation? Restart it 27. How does the operator of a defibrillator ensure there is a good electrical contact with the patients chest? Uses a gel Removes clothing 28. Give two advantages of having charged paint droplets in an electrostatic paint sprayer? Less waste and therefore less cost More even finish 29. Why does the paint spread out on leaving the electrostatic paint sprayer? The positively charged paint droplets repel each other. 30. Why are bicycle frames / cars given the opposite charge to the paint? So that the positively charged paint droplets stick to the frame/car 31. Why is an electrostatic precipitator placed in power station and factory chimneys? Reduce pollution and removes harmful particles 32. What type(s) of power station need an electrostatic precipitator? Fossil fuels 33. What should you look for if a lamp does not light? Is there a gap in the circuit 34. What effect does a variable resistance have on the brightness of a lamp? It can either increase resistance or decrease resistance. Decreasing resistance, increases current and increases the brightness of the lamp In parallel 35. How should a voltmeter be placed into a circuit? 36. What type of wire brings the electrical supply into the house? Live (brown) 37. What type of wire provides the return path for the electrical supply in the house? Neutral (blue) 38. What are the colours and roles of the 3 different wires in a plug? Live (brown) – carries high voltage into the house Neutral (blue) – completes the circuit Earth (yellow/green) – connect to case to prevent it becoming live 39. If there are only 2 wires in a plug which ones are included? Why could only 2 wires be in the plug? Brown and blue. Why? Because the Earth wire is not needed with a ‘double insulated’ appliance 40. Which wire is the safety wire? A fuse 41. Why is a fuse a good safety device? The fuse is a thin wire which melts if the current is too high. This stops the current flowing and avoids damage or electrocution. 42. How do you know which fuse to choose? Choose a fuse with a slightly high amps (A) than the normal current of the appliance. 43. What is ultrasound? A high frequency pressure wave containing compressions and rarefractions. 44. What is meant by a longitudinal wave? The wave direction is parallel to the vibrations 45. What is meant by the frequency of a wave? The number of waves over a set period of time. 46. Explain how sound travels through the air to reach your ear Air particles vibrate. Compressions of air particles in between periods of rarefraction send the sound to the ear. 47. How does the frequency of a note change if its pitch increases? (goes higher) The frequency increases 48. What happens if you change the amplitude of a wave? The sound becomes louder 49. Give two other uses of ultrasound than for baby scans Investigate tumours Measure the speed of blood flow 50. What is the advantage of a pregnant woman having an ultrasound scan? Ultrasound does not harm living cells like an x ray. Ultrasound have good resolution – you can measure tissues. Diagnosis is identifying a problem Therapy is the treatment 51. In medicine, what is the difference between diagnosis and therapy? 52. Give one similarity and one difference between x-rays and gamma rays. Both ionising electromagnetic waves Have similar wavelengths 53. Why are X-rays and gamma rays suitable to treat cancer patients? They kill cells 54. Why are alpha and beta particles not suitable to treat cancer patients? Alpha radiation is absorbed by the skin Beta radiation doesn’t pass through bone. 55. Give another use (than radiotherapy) of gamma radiation in hospitals Sterilising medical instruments and equipment (make very clean) 56. What is a radioactive tracer? A substance used to investigate a patient’s body without surgery 57. Why is a radioactive tracer used? You can detect the tracers movement with a gamma camera. Allows you to identify where there is a problem without the need for surgery. The tracer would be in the body whilst it is tracked. The tracer won’t last in the body and potentially cause problems. Gamma rays 58. Why would a short half life be useful for a radioactive tracer? 59. Which type of nuclear radiation is stopped by several sheets of paper? 60. What is meant by background radiation? Radiation always present in the environment 61. Suggest two natural sources of background radiation Cosmic rays from space Man-made sources from hospitals and industry Present in rock 62. Why is alpha radiation more suitable than either gamma or beta radiation for use in a smoke alarm? Alpha particles are blocked by smoke meaning the current can’t pass through and the alarm sounds 63. Explain how the smoke alarm works Without smoke, alpha particles leave ions in the air which allow a current to pass around inside. With smoke the alpha particles are blocked and the current can’t travel. An alarm sounds. The source of energy provides heat to boil the water to produce steam. The pressure of the steam turns the turbine which turns the generator making electricity. 64. Explain how a power station makes electricity 65. What element is used as the fuel in a nuclear power station? Uranium fuel rods 66. What is meant by fission? Splitting of a nuclei 67. What is the difference between a nuclear reactor in a power station and a nuclear bomb? Nuclear reactor is a controlled fission (splitting) A bomb is uncontrolled 68. How can materials be made radioactive? Bombard the atoms with neutrons 69. Suggest one method of disposing of lower level radioactive waste The waste is covered in concrete and put in the sea. 70. How can you get an electrostatic shock? If you become charged and then become earthed. 71. What happens if you put like charges together? They repel 72. What happens if you put unlike charges together? They attract 73. What causes electrostatic events (phenomena)? Transfer of electrons 74. How do you have a positive charge? Due to an excess of electrons 75. How do you have a negative charge? Due to a lack of electrons 76. Explain how static electricity can be dangerous. (2) Explosions can occur if static electricity occurs in inflammable gases or with high concentrations of oxygen. In situations where large amounts of charge can flow through the body to earth 77. Explain how static electricity can be annoying (2) 78. How can you reduce the chance of getting an electric shock? 79. Explain how static electricity can be useful for electrostatic dust precipitators to remove smoke particles from chimneys 80. Explain how static electricity can be useful for paint spraying 81. Explain how static electricity can be useful for restarting the heart Dirt and dust can become attracted to Tv monitors Cause clothing to cling. Correct earthing Use of insulating mats Using shoes with insulating soles Bonding fuel tanker to aircraft Dust passes through charged metal grids Dust particles become charged Plates are charged opposite to grid Dust particles are attracted to plates Plates stuck and dust falls to collector Spray gun charged Paint particles charged the same so repel giving a fine spray/coat Object charged oppositely to paint Attracts paint to the object giving an even coat with less waste Paddles charged Electrical contact with patient’s chest Charge passed through patient to make heart contract 82. What happens to the resistance/current in a circuit if you make a wire longer? The resistance becomes greater The current is lowered 83. What happens to the resistance/current in a circuit if you make a wire thicker? The resistance is reduced The current increases 84. What is resistance measured in? (think that there is more space for the electrons to pass through and they do so easier) Ohms 85. A ‘double insulated’ appliance means what? It does not need to be earthed. The appliance is a non-conductor and cannot become live. 86. How to calculate the distance using echos? Use the echo time and speed of sound. Remember to divide by two as the sound goes to the object and back. 87. Recognise that ultrasound can be used in medicine for diagnostic purposes (find out what is there) Look inside people by scanning the body Measure the speed of blood flow in the body 88. Describe the features of longitudinal waves 89. Why can we not hear ultrasound? 90. Give uses of ultrasound 91. How can we measure radioactivity? Wavelength (how long between waves) Frequency (the number) Compression (region of higher pressure) Rarefraction (region of lower pressure) The frequency is higher than the upper threshold of human hearing (20,000 Hz) Detecting babies Diagnose problems inside the body Produce images of soft tissues Break down kidney stones Measure the number of nuclear decays emitted per second 92. What makes an ion? Either losing an electron or gaining an electron 93. What happens to a nucleus when an alpha particle is emitted? Mass number decreases by 4 The atomic number decreases by 2 94. Describe what happens to a nucleus when a beta particle is emitted 95. How are tracers used? 96. Where does background radiation comes from? Nucleus has 2 fewer neutrons and 2 fewer protons. Mass number is unchanged The nucleus has one less neutron, nucleus has one more proton. New element is formed. To track waste dispersal To find leaks/blockages in underground pipes To track the passage of food/liquid in the body – look for blockages Rocks and cosmic rays Some from industry and hospitals 97. What sources are used in smoke detectors? Alpha sources 98. How does a smoke detector work? Smoke particles hit by alpha radiation Less ionisation of air particles Current is reduced causing alarm to sound 99. Explain how radioactive dating of rocks works Work out the uranium/lead ratio. 100. Explain how measurements of the activity of radioactive carbon can be used to work out the age of a material 101. Describe some similarities between x-rays and gamma rays 102. How is nuclear radiation used in medicine? When an object dies exchange of air stops As the carbon-14 decays in the sample The ratio from living matter is used to calculate the age within known limits Both are ionising electromagnetic waves Have similar wavelengths Produced in different ways Treatment of cancer using gamma rays Sterilisation of equipment 103. What radioactive particles can pass through skin? Beta and gamma rays 104. Describe some differences between x-rays and gamma rays X-rays are made by firing high speed electrons at metal targets X-rays are easier to control the gamma rays. 105. Describe how electricity is generated at a nuclear power station Nuclear reaction Produces heat Heating water produces steam Spin a turbine Driving a generator Uranium nucleus hit by neutron Causes nucleus to split Energy released More neutrons released A nuclear bomb has radioactive chain reactions that have gone out of control 106. How does uranium release energy 107. What is different about a nuclear bomb and a nuclear reactor for electricity? 108. Explain what is meant by a chain reaction 109. How do scientists stop nuclear reactions going out of control? Uranium nucleus splits more than one neutron is given out These neutrons can cause further uranium nuclei to split Roads placed in the reaction Absorb some of the neutrons Allowing enough neutrons to remain to keep the process operating Fusion happens when 2 nuclei join together Fusion produces large amount of heat energy Fusion happens at extremely high temperatures 110. Describe how nuclear fusion releases energy 111. Describe why fusion for power is difficult Needs high temperatures High temperatures have to be safely managed 112. How does fusion happen in stars? Extremely high temperatures and pressures